- Fix headers to include less or smaller header files.
- Fix header and source files to include missing header files to avoid
  warnings and errors.

diff --git a/include/mmsystem.h b/include/mmsystem.h
index 8c974a0..a86b5ff 100644
--- a/include/mmsystem.h
+++ b/include/mmsystem.h
@@ -8,6 +8,7 @@
 #ifdef __cplusplus
 extern "C" {
 #endif 
+#include "wintypes.h"
 
 typedef LPSTR		    HPSTR;          /* a huge version of LPSTR */
 typedef LPCSTR			HPCSTR;         /* a huge version of LPCSTR */